test: correct typing

Author: ianhi

tests/test_attributes.py

@@ -66,6 +66,7 @@ def test_update_no_changes() -> None:
 @pytest.mark.parametrize("group", [True, False])
 def test_del_works(group: bool) -> None:
     store = zarr.storage.MemoryStore()
+    z: zarr.Group | zarr.Array
     if group:
         z = zarr.create_group(store)
     else:
@@ -75,6 +76,7 @@ def test_del_works(group: bool) -> None:
     del z.attrs["a"]
     assert dict(z.attrs) == {"c": 4}
 
+    z2: zarr.Group | zarr.Array
     if group:
         z2 = zarr.open_group(store)
     else: